1. Field of This Invention
This invention relates to a process for the production of chloroacetyl chloride.
2. Prior Art
The production of chloroacetyl chloride (CAC) by conversion of ketene with chlorine in widely diverse solvents is known. Examples of such solvents are alkylacetate (British Pat. No. 782,773), SO.sub.2 (U.S. Pat. No. 2,889,365), alicyclic carbonate, alkoxyalkyl ester, glycol ester (German OS No. 2,247,764), sulfones (U.S. Pat. No. 3,882,173), phosphate ester (U.S. Pat. No. 3,883,589) and lactones (German OS No. 2,247,765). When most of these solvents are used, dichloroacetyl chloride (DCAC) is obtained as a by-product in quantities of 2 to 6.5 percent. However, since the presence of a large portion of dichloroacetyl chloride in chloroacetyl chloride is detrimental in many types of usage, the art nowadays requests chloroacetyl chloride containing only 0.1 to 0.3 percent of dichloroacetyl chloride. The removal of dichloroacetyl chloride from chloroacetyl chloride by simple distillation is virtually impossible because they have essentially equal boiling points.
U.S. Pat. No. 3,763,023 teaches separation by means of azeotropic distillation. Azeotropic distillation has various disadvantages, such as, high investment requirements, high operating costs and sensitivity to fluctuations in product composition.
When lactones or phosphate esters are used as solvents, the desired low levels of dichloroacetyl chloride are achieved. But there are disadvantages in the use of such solvents as they are relatively expensive and such solvents cannot be completely recovered. The losses of solvent are relatively great -- experiments resulted in losses of 10 to 15 percent, depending on the lactone or phosphate ester used.
Dichloroacetyl chloride has been removed by chemical conversion with water or alcohols, whereby the dichloroacetyl chloride preferably reacts to dichloroacetic acid or ester (German Pat. No. 2,313,405). Since this reaction however is not selective and chloroacetyl chloride can enter into the reaction, a high degree of loss of chloroacetyl chloride results.